Often during the delivery of medical care it is necessary to ensure adequate ventilation of the ill or anesthetized patient who is unable to sustain adequate respiration. The term airway management refers to the methods by which ventilation is provided to such patients, e.g., Stone, D. J. and Gal, T. J., in Anesthesia 4.sup.th Edition, Miller, R. D., ed., Chapter 42, Churchill-Livingston, Inc., New York (1994).
A common form of airway management involves the insertion of a tube into the pharynx and larynx of a patient for the purpose of establishing an unobstructed airway into the lungs, a process called intubation. Laryngoscopy, a first step in the intubation process, allows visualization of the pharynx and larynx during the intubation procedure. A laryngoscope is an instrument which facilitates the laryngoscopy procedure.
Typically, the laryngoscope includes a blade and a handle. The blade is inserted into the pharynx of the patient through the mouth and the handle is held by the operator and used to control the position of the blade. The blade may be detachably mounted to the handle, e.g., U.S. Pat. No. 2,630,114.
Laryngoscopy and intubation are powerful noxious stimuli, each individually being capable of eliciting a severe adverse cardiovascular response. In fact, deeper levels of anesthesia are required to blunt the body's response to laryngoscopy and intubation than are required to blunt the response to a surgical incision, e.g., Yakaitis et al., Anesthesiology, 47:386(1977), and Yakaitis et al., Anesthesiology, 50:59(1979). Deepening the level of anesthesia, giving intravenous cardiovascular drugs, performing local anesthesia nerve blocks, and applying topical anesthetics directly to the oral airway, pharynx, and larynx are all common techniques for lessening the adverse consequences of laryngoscopy and intubation. Topical administration of local anesthetics has the most specific action and the least side effects.
Typically, nothing is done to ablate the response to the insertion of the laryngoscope blade into the oral airway of the patient. Only in extreme cases is an anesthetic spray administered into the mouth prior to blade insertion.
To ablate the response to the insertion of the endotracheal tube, the pharynx and larynx are sprayed with a topical anesthetic spray. Currently, the administration of the anesthetic spray during laryngoscopy requires the use of a two-step, two-handed procedure: the laryngoscope blade is first inserted into the mouth of the patient, then, once a view of the larynx is established, holding the laryngoscope with one hand, the operator sprays the pharynx, larynx, and trachea with a topical anesthetic, using his other hand to hold the anesthetic container and dispense the anesthetic. This second step usually requires the operator to look away from the larynx to pick up the local anesthetic dispenser. While looking away, it is not uncommon for the operator to lose his view of the pharynx and larynx, requiring him to reestablish such view, thereby complicating the intubation procedure. Because this procedure is performed while the patient is not breathing, it is important that it be performed as quickly as possible.
One solution to the problem of simplifying the administration of the topical anesthetic spray while operating a laryngoscope is disclosed by Breslau in U.S. Pat. No. 4,432,350 (Breslau). Breslau describes a laryngoscope having a reservoir for containing a topical anesthetic mounted to the handle and a conduit for delivering the anesthetic to the tip of the blade. The anesthetic is expelled from the reservoir by compressing the outer walls of the reservoir directly or with a delivery means mounted to the handle.
While the Breslau laryngoscope apparently provides a system whereby laryngoscope operation and anesthetic administration may be performed with one hand, several significant problems exist with Breslau's apparatus which have contributed to its lack of acceptance by the medical community.
In many situations it is necessary to apply a large force to the blade of the laryngoscope in order to afford an adequate view of the patient's pharynx. In these situations, the operator must grip the handle of the laryngoscope firmly with a large compressive force. While the force is being applied, the hand must remain motionless or the view of the larynx can be lost. Thus, if an anesthetic reservoir and/or delivery means is attached to the handle, it will interfere with the operator's ability to firmly grip the laryngoscope, and therefore lead to loss of proper positioning of the laryngoscope blade. Moreover, when applying a large compressive force to the handle, it is possible to inadvertently expel the anesthetic, thereby greatly complicating the procedure and even possibly harming the patient.
Another drawback of the Breslau laryngoscope is that several assembly steps are required prior to use. When a disposable blade is used, the blade must first be attached to the handle, then the reservoir must be attached to the handle, and finally the delivery conduit must be threaded along the blade such that the outlet of the conduit is precisely aligned with the distal end of the blade. Clearly this sort of multi-step assembly is not practical under time-critical circumstances.